(1) Field of the Invention
The present invention generally relates to an electrophotographic recording apparatus having a magazine unit for storing developer such as toner, and more particularly to an electrophotographic recording apparatus having a magazine unit for storing developer that can be easily replaced by a user.
(2) Description of Related Art
In a general electrophotographic recording apparatus, an electrostatic latent image is formed, by an optical writing process, on a precharged photosensitive member (e.g. a belt shaped photosensitive member), toner (developer) is then adhered to the electrostatic latent image by a developing unit so that a toner image is formed on the photosensitive member. The toner image is transferred from the photosensitive member to a recording sheet fed to the photosensitive member. The recording sheet is heated so that the toner thereon is fused and fixed. After this, the recording sheet on which the toner image is fixed is ejected from a housing of the electrophotographic recording apparatus.
After the toner image is transferred to the recording sheet, an amount of toner remains on the photosensitive member. The toner remaining on the photosensitive member is referred to as residual toner. The residual toner is scraped from the photosensitive member and then withdrawn as scrap toner. A residual charge on the photosensitive member is discharged by lighting.
Recent electrophotographic recording apparatus of this type can perform hundreds or thousands of printings, in a case where A4 sized recording paper is used, without changing the photosensitive member and the developing unit. However, as miniaturizing has been required recently, a toner supply tank used for supplying toner to the developing unit and a toner withdrawing tank used for withdrawing the scrap toner cannot be made large. Thus, users of this type of electrophotographic recording apparatus must resupply new toner thereto and withdraw the scrap toner.
Thus, the inventors of the present application have proposed a cleaner-toner-magazine (CTM) in which the tone supply tank and the toner withdrawing tank are integrated with each other. The CTM can be changed to a new one so that operations for resupplying new toner and for withdrawing the scrap toner become simple.
A description will now be given of the CTM which has been proposed by the inventors with reference to FIGS. 1 and 2.
Referring to FIG. 1, which shows a recording unit having the CTM, a photosensitive belt 1 circularly moves at a constant speed in a direction shown by the arrow. A precharger unit 2, a developing unit 7 and a transfer charger unit 9 are arranged around the photosensitive belt 1 in this order according to the electrophotographic process. The precharger unit 2 uniformly electrifies a surface of the photosensitive belt 1. An optical writing part 3 is provided between the precharger unit 2 and the developing unit 7. A laser beam is emitted from a laser unit 4 modulated in accordance with image signals. The laser beam passes via a polygonal mirror 5 and a mirror 6 and projects onto the surface of the photosensitive belt 1 via the optical writing part 3. Thus the photosensitive belt 1 is exposed by the laser beam, so that an electrostatic latent image is formed on the photosensitive belt 1. The developing unit 7 supplies toner to the photosensitive belt 1 in order to develop the electrostatic latent image. The toner supplied to the photosensitive belt 1 is adhered to the electrostatic latent image so that a toner image is formed on the photosensitive belt 1. A paper cassette 14 having recording papers is detachably mounted in a housing (not shown) of the recording unit. The recording paper is fed one by one from the paper cassette 14 toward the transfer charger unit 9. The toner image is transferred from the photosensitive belt 1 to a recording paper by the transfer charger unit 9. The recording paper passing through the transfer charger unit 9 is supplied to a fuser unit 10 so that the toner image is fused and fixed onto the recording paper. The recording paper is then ejected from the housing of the recording unit.
A CTM (Cleaner-Toner-Magazine) 20 is mounted on a downstream side of the transfer charger unit 9 in a direction in which the photosensitive belt 1 is circularly moved. The CTM 20 has a toner supply chamber 8 and a toner withdrawing chamber 12. A cleaning blade 11 is provided in the toner withdrawing chamber 12 so as to scrape the residual toner from the photosensitive belt 1. The residual toner scraped by the cleaning blade 11 is stored in the toner withdrawing chamber 12 of the CTM 20. Toner has been previously stored in the toner supply chamber 8 of the CTM 20. A discharger unit 13 is provided between the precharger unit 2 and the CTM 20. The discharger unit 13 emits a light onto the surface of the photosensitive belt 1 so that the residual charge is removed from the surface of the photosensitive belt 1.
The CTM 20 can be easily replaced by a user. However, as the CTM 20 and the developing unit 7 are separated from each other, mechanisms for conveying toner from the toner supply chamber 8 of the CTM 20 to the developing unit 7 must be provided. The mechanisms are formed, for example, as follows.
An ejecting mechanism 22 is provided in the toner supply chamber 8 of the CTM. The ejecting mechanism 22 has a conveyor for conveying the toner in the toner supply chamber 8 toward an outlet 21 which is formed on a side end of the toner supply chamber 8. Thus, the toner in the toner supply chamber 8 is ejected therefrom via the outlet 21 by the ejecting mechanism 22. A conveyor mechanism 23 is provided between the outlet 21 of the toner supply chamber 8 and an inlet of the developing unit 7. Thus, the conveyor mechanism 23 conveys the toner from the outlet of the toner supply chamber 8 of the CTM 20 to the inlet of the developing unit 7. A supplying mechanism 24 is provided in the developing unit 7. The supplying mechanism 24 has a conveyor extending in a direction approximately parallel to a width of the photosensitive belt 1. That is, the supplying mechanism 24 conveys the toner from the inlet in a main scanning direction s that the toner can be supplied, uniformly distributed in the main scanning direction, from the developing unit 7 to the photosensitive belt 1.
FIG. 2 shows a modification of the recording unit having the CTM 20.
Referring to FIG. 2, the CTM 20 is mounted so that the toner supply chamber 8 and the developing unit 7 are arranged in a direction approximately parallel to a vertical direction. The outlet 21 of the toner supply chamber 8 of the CTM 20 and the inlet of the developing unit 7 are connected to each other by a duct 26. The toner is supplied, by free fall, from the toner supply chamber 8 to the developing unit 7 via the duct 26. By implementing the modification shown in FIG. 2, the conveyor mechanism 23, shown in FIG. 1, for conveying the toner from the toner supply chamber 8 to the developing unit 7 can be omitted.
In the recording units shown in FIGS. 1 and 2, when the toner in the toner supply chamber 8 of the CTM 20 is used up, the toner withdrawing chamber 12 of the CTM 20 is filled with the scrap toner. In this state, the CTM 20 is changed to a new one. That is, by changing only the CTM 20, new toner can be resupplied to the recording unit and the scrap toner can e withdrawn therefrom.
Conventionally, however, a process for supplying the toner from the toner supply chamber 8 of the CTM 20 to the developing unit 7 has not been definitely decided upon. In addition, users cannot know that the toner in the toner supply chamber of the CTM is used up until the quality of images formed on the recording sheets deteriorates.